Frank Haunert

Highly selective glycosylated prodrugs of cytostatic CC-1065 analogues for antibody-directed enzyme tumor therapy.

Novel prodrugs of the cytotoxic antibiotic CC‐1065 for an antibody‐directed enzyme prodrug therapy (ADEPT) were prepared that show an excellent selectivity with a high toxicity of the corresponding drug. In particular, the seco‐CBI analogue of CC‐1065, 1‐chloromethyl‐5‐hydroxy‐1,2‐dihydro‐3H‐benz[e]indole, as well as the novel methyl‐seco‐CBI analogue 1‐(1′‐chloroethyl)‐5‐hydroxy‐1,2‐dihydro‐3H‐benz[e]indole, were synthesized and transformed into their galactosides 10 a and 10 b, respectively. These galactosides can be cleaved with β‐D‐galactosidase to give the free cytotoxic compounds. They were tested in in vitro cytotoxicity assays by using human bronchial carcinoma cells of line A549 in the presence and in the absence of β‐D‐galactosidase. While the seco‐CBI prodrugs revealed only modest selectivity, prodrugs of the methyl‐seco‐CBI analogue bearing an anti orientation of the substituents at the two stereogenic centers of the N‐heterocycle displayed an excellent selectivity with an ED50 quotient of about 750. The cytotoxicity of the corresponding phenol was rather high, with an ED50 of 1.3 nM. The diastereomer with a syn orientation at the stereogenic centers was much less toxic.

A strategy for tumor-selective chemotherapy by enzymatic liberation of seco-duocarmycin SA-derivatives from nontoxic prodrugs

Immuno-conjugates obtained by linking enzymes with appropriate monoclonal antibodies, which bind to tumor-associated antigens, can be employed in a tumor-selective antibody directed enzyme prodrug therapy (ADEPT). For this strategy the glycosides 17a--c were prepared as prodrugs of CI-TMI 14 which is a structurally simplified analogue of the highly potent antitumor agent duocarmycin SA 2. Exposure of 17a--c to cultured carcinoma cells of line A549 displayed a very low toxicity; however, after addition of the corresponding enzymes and exposure for 24 h at prodrug concentrations of <0.1 microM the proliferation of the carcinoma cells was inhibited almost completely with ED(50prodrug)/ED(50drug) of up to 270 in the presence and in the absence of the enzyme. The synthesis of 17a--c was achieved by transformation of nitroanisidine 6 into 12 which was glycosidated to give 16a--c. Removal of the silyl groups, introduction of a chlorine atom and solvolysis of the acetal groups led to 17a-c, of which 17a and 17c are promising candidates for further elaboration.

Regioselective Reduction and Ring Cleavage of Polycyclic Barbituric Acid Analogues Derived from Intramolecular Hetero-Diels−Alder Reactions

The annulated and bridged dihydropyrans 6−8 obtained by a domino-Knoevenagel-hetero-Diels−Alder reaction with N,N′-dimethylbarbituric acid were reduced with excess DIBAL-H at −78 °C to give the corresponding 3-desoxy derivatives, which were then hydrolyzed to the lactones 14−16 with HCl. Compounds 15 and 16 were further reduced to the corresponding lactols. Elimination finally yielded the new functionalized heterocycles 18 and 20.